We had an enquiry from a customer running a temperature-controlled process that only needed to be monitored within a narrow band — a jacketed reactor held between roughly 80–90°C. Their existing wide-range RTD transmitter covered 0–200°C, and the reading barely moved across the whole 4-20mA span, so small but important temperature changes were hard to see on the control system.
This is a resolution problem, not a wiring problem. A transmitter set up for a wide input span spreads its 4-20mA output across that whole range, so a narrow process band only uses a small slice of the signal — fine control becomes difficult, and the PLC or DCS effectively loses precision even though the sensor itself is accurate. What’s needed is a transmitter that can be spanned down to match the actual process band, without losing accuracy at that narrow range.
For this, we would normally recommend the MTT MS3702B, a slim plug-in RTD temperature transmitter built to hold accuracy on narrow measurement spans, down to as little as 30-50°C depending on the RTD type. It accepts Pt100Ω, JPt100Ω, or Pt50Ω RTD inputs, and linearizes the signal into a clean 4-20mA, 0-20mA, or DC voltage output — available as a single output or isolated dual output. Like the rest of the plug-in range, it mounts on its own DIN-rail socket base for fast swap-out, and standard upscale sensor burnout protection flags a broken RTD rather than letting the reading drift to a misleading value.
Before we quote, we would normally check:
- The actual process temperature band you need to monitor (not just the sensor’s full range)
- RTD element type (Pt100, JPt100, or Pt50)
- Whether you need a single output or isolated dual output
- Output signal range required (4-20mA, 0-20mA, or voltage)
- Power supply available at the panel (AC or DC)
Hope this helps — send us your process temperature band and RTD type, and we can confirm the right model.
| Input Types | Pt 100Ω, JPt 100Ω, or Pt 50Ω |
| Temperature Range | -200 to +850°C (Pt 100Ω); -200 to +500°C (JPt 100Ω); -200 to +600°C (Pt 50Ω) |
| Minimum Input Span | 30-50°C (Pt 100Ω/JPt 100Ω); 60-100°C (Pt 50Ω) |
| Excitation Current | Approximately 1mA for Pt type at 0-100°C |
| Lead Wire Resistance | 200Ω maximum per wire |
| Output | 0-20mA DC, 4-20mA DC, or DC voltage ranges from 0-10mV up to ±10V (single or isolated dual output) |
| Isolation | 4-way isolation between input, Output 1, Output 2, power, and ground |
| Power Supply | 100-240V AC (47-63Hz), 24V DC ±10%, or 100-240V DC |
| Accuracy | Better than ±0.15% of span (at 25°C±5°C) |
| Temperature Effect | Better than ±1.0% of span per 10°C ambient change |
| Response Time | 240ms maximum (0-90%) |
| CMRR | Minimum 100dB |
| Insulation Resistance | 100MΩ minimum at 500V DC |
| Dielectric Strength | 2000V AC for one minute |
| Sensor Burnout Protection | Upscale, standard |
| Dimensions (W x H x D) | 29mm x 86mm x 125mm |
| Weight | Main unit up to 120g; socket up to 80g |
| Mounting | Wall or DIN rail mounting, plug-in socket base |
| Terminals | M3.5 screw terminals |
| Operating Temperature | -5 to 55°C ambient (storage: -10 to 60°C) |
| Operating Humidity | 5-90% RH, non-condensing |
Frequently Asked Questions
What is the MTT MS3702B used for?
It converts a Pt100, JPt100, or Pt50 RTD temperature signal into a standard 4-20mA, 0-20mA, or DC voltage output, built to stay accurate even on a narrow process temperature band.
Can the MS3702B be used for a wide temperature range instead?
It can, but it’s specifically built to hold accuracy on narrow spans (as tight as 30-50°C). If your process covers a wide temperature range, the standard MS3702 is usually the better fit — tell us your process range and we’ll confirm.
What’s the difference between the MS3702B and the standard MS3702?
Both are RTD transmitters, but the MS3702B is tuned to hold accuracy on a narrow measurement span, while the standard MS3702 has a tighter temperature-effect spec for general-purpose wider-range use. Which one is right depends on how narrow your actual process band is.
What’s the difference between the MS3702B and the MS3702-01?
The MS3702-01 is built for 4-wire RTD sensors, which removes lead wire resistance error on long cable runs. The MS3702B is a standard 2/3-wire unit tuned for narrow-span accuracy. Match the model to your wiring type and process range.
How do I know which MS3702 model I need?
Tell us your RTD wiring type (2, 3, or 4-wire), the actual temperature band your process runs in, and the output signal your PLC or DCS expects. We’ll confirm the right model before you order.
Download MTT MS3702B Slim Plug-In RTD Temperature Transmitter information here
Spec Sheet: MTT MS3702B Spec Sheet
Manual: MTT MS3702B Manual
